U.S. Pat. No. 5,270,091 to Krysiak is directed to a window strip for use in fabricating insulated glass. Such strips have been problematic however, because they require a compression resistant spacer and a deformable sealant, and such a design is not well suited to handle the stresses (i.e., temperature cycling, wind forces, and the like) which are commonly encountered by insulated glass units.
U.S. Pat. No. 4,109,431 to Mazzoni is directed to a complex "sealing and spacing unit for multiple glazed windows" comprising a moisture impervious base layer which is wrapped around the outer peripheral surfaces of two parallel (spaced apart) glass panes, a spacer-dehydrator inserted between the glass panes, a thin layer of non-mastic adhesive which secures the spacer dehydrator to the base layer and a cold flowable mastic to seal the base layer to the peripheral outer surfaces of the glass panes.
Pressure sensitive adhesives (PSAs) in general are well known. One broad class of such adhesive compositions are "rubber based" PSAs, typically comprising tackifier and one or more (low glass transition temperature, i.e., less than about 0.degree. F.) rubbery base polymers. Common rubber based pressure sensitive adhesive compositions include those comprising isobutylene homopolymer or copolymer. Isobutylene polymers not only have excellent flow onto many substrates, but also, the polymers will generally crystallize as they are stretched and pulled from a substrate, thereby providing exceptional peel strength.
However, rubber based PSAs are not without their shortcomings. First, such materials generally have difficulty flowing onto (penetrating) glass, acrylics (i.e., automotive paints), polyethylene, ceramics, and the like. Second, regardless of surface penetration, the rubber based PSAs will generally have difficulty "anchoring" or "holding" onto a substrate, where there is chemical incompatibility between the PSA and the substrate.
Another broad class of pressure sensitive adhesives are known as "acrylic" PSAs. In many instances, acrylic PSAs have excellent flow and compatibility with polar substrates, relative to rubber based PSAs (and also generally can be formulated without tackifier). However, acrylic PSAs can be expensive, can be difficult to formulate for creep resistance, can be difficult to formulate for resistance to moisture, can be difficult to adhere to non-polar or low surface energy surfaces, and must generally be applied as a liquid or semi-liquid.
A need therefore exists for pressure sensitive adhesives having many of the advantages of conventional (acrylic and rubber based) PSAs, without many of the disadvantages.
A conventional rubber based PSA is polyisobutylene or "PIB." Another conventional such material is commonly referred to as "butyl" or "butyl rubber" and is derived from isobutylene and a relatively small amount of isoprene; the isoprene is generally used to provide unsaturation to the isobutylene polymer, thereby allowing the resulting polymer to be crosslinked (or crosslinkable). Butyl rubbers can be brominated or chlorinated.
Brominated para-methyl styrene/isobutylene copolymers have been developed by and are commercially available through the EXXON Chemical Company of Houston Tex., U.S.A. (see generally, U.S. Pat. No. 5,162,445 to POWERS). These polymers are taught to be crosslinked by conventional high temperature post curing.
U.S. Pat. No. 5,242,727 to BRIDDELL is directed to a roofing membrane adhesive, and in one embodiment, BRIDDELL teaches the use of a halogenated copolymer of p-methylstyrene/isobutylene. BRIDDELL teaches conventional high temperature post curing and is directed to EPDM based compositions.
Apart from adhesion, certain preferred polymers can be designed to provide compatibalization between dissimilar polymers and can therefore be useful in the art of blending or alloying dissimilar polymers or compositions. Polymer blending and alloying in generally is known, and compatibilizers in general are also known. However, the polymers of the present invention are far removed from conventionally known compatibilizers, and in certain embodiments, polymers of the present invention can provide a whole new class of advantageous polymer blends and alloys.